The proposed research addresses the neuronal mechanisms involved in resolving the location of sound sources, and in suppressing perception of echoes. These issues have specific relevance for our understanding and treatment of hearing deficits, and could also have general implications for our understanding of brain function. The research goals will be addressed using a combined behavioral and neurophysiological approach, exploiting the spatial topography of the barn owl's auditory midbrain, which enables efficient characterization of the entire neuronal representation of a sound. Behavioral experiments will measure the extent to which the ability to resolve the location of sounds is impaired for echoes. Comparable measures of behavioral and neuronal discrimination performance will be derived using signal detection theory. The neuronal basis for discriminating sound source location will be determined by comparing the discrimination performance of single neurons and of neuronal populations to behavioral performance, measured previously. Finally, the neuronal basis of echo suppression will be addressed by comparing the effects of a direct sound source on neuronal and behavioral discrimination of sound source location.